Filter



Nov. 1, 1938. c. A. CAMPBELL FILTER Original Filed OCt. 15, 1937 3nventor (Ittomegs Patented Nov. 1, 1938 UNITED STATES PATENT OFFICE FILTER Application October 13, 1937, Serial No. 168,825

Renewed September 29, 1938 v 3 Claims.

This invention relates to air filters and particularly to such devices intended for use in brake cylinders or the like. The invention, however, is susceptible of use in filtering air, where the flow occurs under moderate pressure, and where economy and ease of replacement are important factors.

In the air brake art it is now standard practice to apply a breather to the guiding head (sometimes called the non-pressure head) of thebrake cylinder, .and to protect this with a filter so that the entrance of dust and cinders isminimized or prevented. The present invention provides a filter which is inexpensive to construct and easy to fix in position.

The invention will now be described by reference to the accompanying drawing, in which;-

Fig. l is a half elevation of a brake cylinder partly broken away to show the location and construction of the filter.

Fig. 2 is a face view of the filter shown in Fig. 1.

Fig. 3 is a section on the line 3--3 of Fig. 2.

Fig. 4 is a section of the front head of the brake cylinder, looking downward relatively to Fig. 1.

In Fig. l the brake cylinder is indicated at 6, the rear or pressure head at I, the front head at 8, the piston rod at 9. This rod is attached to piston I I and is guided in the front head 8. The piston return spring is shown at I2. These parts may be of any usual construction except that the front head 8 is provided with a breather port and filter seat which will now be described.

The head 8 is provided with an outwardly convex bulge I3 surrounded on the inner side of the head by a circular seat rim I4 to receive a disc shaped filter unit. This unit is made up of a layer I5 of coarse fabric, preferably felt, and a layer I6 of finer fabric preferably also felt, backed by a foraminous metal plate I! preferably of woven brass wire. The parts I5, I6 and H are stitched together by means of spaced wire staples I8. These pass through both layers of fabric and the foraminous plate I1 and are clinched, as indicated. There is a central perforation 20 as indicated in Figs. 2 and 3.

The bulge I3 forms a chamber I9 surrounded by circular rim I4, and from thischamber leads the breather port 2I below which is a drip rim 22. A pin or bolt 23 is driven through a drilled hole in bulge I3 and makes a drive fit therein. The hole is so located that bolt 23 is normal to the plane of circular rim I4 and concentric there-' cotter pin 25 retain the filter disc in place, the hole for the cotter pin being so located that plate IT is slightly sprung or dished, and hence serves as resilient means to compress the edges of the felt layers and produce a good seal on rim M.

The construction has several advantages. The filter unit is simple to construct, has a long life, and is protected from water and from vandals. The filter disc itself includes the resilient means used to seal the filter to its seat and is adequate to maintain the seal throughout the life of the disc. The only machining required is the operation of drilling the hole for bolt 23-all other parts receiving their final form in the casting operation.

Modifications are possible. The use of two layers of felt of different textures is preferred but not essential, and other foraminous plates may be substituted for the woven wire cloth described. The manner of mounting bolt 23 may be modified.

What is claimed is,

1. The combination of an enclosing member having a breather port, and an annular seat surrounding said port; a drip ring for resisting the entrance of water through said port; a retaining pin substantially concentric with and normal to the plane of said seat; a filter unit encircling said pin and engaging said seat, said unit comprising a disc of fabric filtering material and a resilient plate-like foraminous backing; and retaining means reacting between said pin and plate and deflecting the plate to develop elastic sealing stress between the unit and the seat.

2. The combination of an enclosing member having .a breather port, and an annular seat surrounding said port; a retaining pin substantially concentric with and normal to the plane of said seat; a filter unit encircling said pin and engaging said seat, said unit comprising a disc of fabric filtering material and a resilient plate-like foraminous backing; and retaining means reacting between said pin and plate and deflecting the plate to develop elastic sealing stress between the unit and the seat. 7

3. A self-sustaining filter unit comprising a resilient foraminous metal backing plate and a porous fabric facing attached together, said facing being adapted to seal on its peripheral marginal area against an annular seat and said plate being arranged to be stressed at its center to develop an elastic sealing pressure upon the sealing area of the facing when in use, such plate having suflicient rigidity to retain approximately its original unstressed form while stressed to develop such elastic sealing pressure.

CHARLES A. CAMPBELL. 

